The overall objective of the project outlined here is to understand how neuronal properties are incorporated in the central nervous system. The immediate aim is to reate the maturation, and functional role, of corticotectal and intertectal systems to superior colliculus (SC) physiology - and to relate this physiology to behavior. Two related lines of research will be pursued. 1. Physiological and anatomical techniques will be employed in studying maturation. The development of corticotectal projection will be studied with autoradiographic tracing techniques, and its functional development and influence on SC cells will be studied with single-unit recording techniques. 2. The behavioral and electrophysiological consequences of disrupting corticotectal and intertectal systems will also be studied. Presumably, in the intact animal, ipsilateral cortex has a facilitatory influence on the SC which is balanced by the inhibitory influence of the opposite SC via intertectal projections. Extensive ipsilateral cortical damage disrupts this balance and produces contralateral visual neglect. However, a second lesion to the opposite SC or intertectal system reinstates visually guided behavior. The changes in the properties of individual SC cells which accompany these behavioral changes will be studied in order to learn which SC properties are essential for visually-guided behavior.